1. Field of the Invention
The present invention relates to a rubber composition comprising an ethylene/xcex1-olefin/non-conjugated diene copolymer rubber as a major component, exhibiting superior processability, such as roll processability and extrusion processability, excellent tackiness (adhesiveness), and capable of producing vulcanized rubber having excellent mechanical characteristics and low and high temperature properties.
The rubber composition of the present invention can be suitably used for a wide variety of applications such as a hose, sponge material, sealing material, electric insulating material, injection processing material, industrial rubber product, rubber material for vehicles, and the like.
2. Description of the Background Art
Conventionally, ethylene/xcex1-olefin/non-conjugated diene copolymer rubbers have more excellent weather resistance, heat resistance, and ozone resistance than diene-type rubbers due to absence of unsaturated bonds in the main chain and, therefore, are used for a wide variety of applications such as a hose, sponge material, sealing material, injection processing material, rubber material for vehicles, and the like.
The extended area of applications of such products in recent years requires a rubber material exhibiting better properties and processability in both a high temperature region and a low temperature region.
Conventionally, when using an ethylene/xcex1-olefin/non-conjugated diene copolymer rubber as a rubber material exhibiting superior processability, either a low molecular weight copolymer among the ethylene/xcex1-olefin/non-conjugated diene copolymers is used or such a copolymer rubber is used in admixture with a larger amount of process oil.
However, an ethylene/xcex1-olefin/non-conjugated diene copolymer rubber having a small molecular weight results in formed products with poor properties, particularly poor strength. Addition of a large amount of process oil to an ethylene/xcex1-olefin/non-conjugated diene copolymer rubber not only may soil a mold due to bleed-out, but also may cause vulcanization-adhesion defects, resulting in formed products with inadequate properties.
An object of the present invention is to provide a rubber composition comprising an ethylene/xcex1-olefin/non-conjugated diene copolymer rubber, exhibiting superior processability, such as roll processability and extrusion processability, producing formed products with an excellent surface, and exhibiting excellent adhesiveness.
Another object of the present invention is to provide an ethylene/xcex1-olefin/non-conjugated diene copolymer rubber composition capable of producing vulcanized rubber having excellent mechanical characteristics and superior low and high temperature properties.
As a result of extended studies, the inventors of the present invention have found that the above object can be attained if a rubber composition comprises a specific low molecular weight ethylene/xcex1-olefin/non-conjugated diene copolymer rubber and a specific high molecular weight ethylene/xcex1-olefin/non-conjugated diene copolymer rubber in combination. The inventors have further found that processability of the copolymer rubber can be improved if such a rubber composition is combined with a specific ethylene/xcex1-olefin/non-conjugated diene copolymer rubber. These findings have led to the completion of the present invention.
The above object can be achieved in the present invention by a rubber composition comprising (a) a low molecular weight copolymer rubber which is an ethylene/xcex1-olefin/non-conjugated diene copolymer rubber having a limiting viscosity [xcex7] of 0.4-1.6 dl/g measured in decalin at 135xc2x0 C., an ethylene content of 40-60 wt %, and an iodine number of 5-35 and (b) a high molecular weight copolymer rubber which is an ethylene/xcex1-olefin/non-conjugated diene copolymer rubber having a Mooney viscosity (ML1+4, 100xc2x0 C.) of 60-150, an ethylene content of 60-80 wt %, and an iodine number of 5-35, wherein the difference between the iodine number of the low molecular weight copolymer rubber (a) and the iodine number of the high molecular weight copolymer rubber (b) is 5 or less and the ratio by weight of the low molecular weight copolymer rubber (a) and the high molecular weight copolymer rubber (b) is 50/50 to 80/20, the rubber composition having a Mooney viscosity (ML1+4, 100xc2x0 C.) of 20-50.
In the above rubber composition, the difference between the iodine number of the low molecular weight copolymer rubber (a) and the iodine number of the high molecular weight copolymer rubber (b) is preferably 3 or less.
In the above rubber composition, the xcex1-olefin in the low molecular weight copolymer rubber (a) or the high molecular weight copolymer rubber (b) is preferably one or more xcex1-olefins selected from the group consisting of propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-eicosene.
In the above rubber composition, the xcex1-olefin in the low molecular weight copolymer rubber (a) or the high molecular weight copolymer rubber (b) is preferably propylene, 1-butene, or 1-octene.
In the above rubber composition, the non-conjugated diene in the low molecular weight copolymer rubber (a) or the high molecular weight copolymer rubber (b) is preferably one or more non-conjugated dienes selected from the group consisting of 5-ethylidene-2-norbornene, 5-propylidene-2-norbornene, dicyclopentadiene, 5-vinyl-2-norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene, norbornadiene, 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 5-methyl-1,5-heptadiene, 6-methyl-1,5-heptadiene, 6-methyl-1,7-octadiene, and 7-methyl-1,6-octadiene.
In the above rubber composition, the non-conjugated diene in the low molecular weight copolymer rubber (a) or the high molecular weight copolymer rubber (b) is preferably 1,4-hexadiene, dicyclopentadiene, or 5-ethylidene-2-norbornene.
The above object can be achieved in the present invention by a vulcanized rubber product obtained by vulcanizing the above rubber composition using sulfur, a sulfur compound, or an organic peroxide.
In the above vulcanized rubber product, the sulfur or sulfur compound is preferably used in an amount from 0.1 to 10 parts by weight for 100 parts by weight of the copolymer rubber.
The above object can be achieved in the present invention by a rubber composition comprising 30-80 wt % of the above rubber composition and 20-70 wt % of an ethylene/xcex1-olefin/non-conjugated diene copolymer rubber (c) having a Mooney viscosity (ML1+4, 100xc2x0 C.) of 30-90, an ethylene content of 45-60 wt %, and an iodine number of 5-35, provided the total of the rubber composition and the ethylene/xcex1-olefin/non-conjugated diene copolymer rubber (c) is 100 wt % (the ethylene/xcex1-olefin/non-conjugated diene copolymer rubber (c) is hereinafter referred to simply as xe2x80x9ccopolymer rubber (c)xe2x80x9d).
Other objects, features and advantages of the invention will hereinafter become more readily apparent from the following description.